The specific aims will be: (a) determination of the standard molal electrode potentials for Ag-AgCl and Ag-AgBr electrodes in 20, 30, 40 and 50 mass % DMSO-H2O, THF-H2O, glycerol-H2O, diglyme-H2O, monoglyme-H2O, DMF-H2O, and ethanol-H2O, at 25, 0, -5, -10, -15 and -20 degrees C; (b) calculation of standard pH*(s) values for reference buffers, such as Tricine, Bicine, bes, Pipes, Ada, and Hepes (which have been previously studied in aqueous media as part of a prior NIH grant) in the same mixed solvents at the same temperatures as (a); (c) establishment of an operational definition of pH* using emf cells with liquid junction (consisting of hydrogen and calomel electrodes) and the pH*(s) values from similar cells without liquid junction; (d) calibration of conventional glass-calomel pH cells for use in making meaningful and reliable pH measurements inmixed solvents at subzero temperatures. The methodology inovlves three basic steps: (1) The first step is the measurement of the emf of the cell with the reference buffer solution in mixed solvent media, both with and without liquid junction. (2) The second step is the determination of psHo, which is the limit approached by psH for each buffer solution as the halide molality (mx) is extrapolated to zero. (3) The final step is to calculate the standard pH values by using the expression pH(s) = pSHo + log Gamma x, in which the activity coefficient of the halide ion (Gamma x) is obtained from a conventional definition, as was done previously in a prior NIH grant. The long-term objectives are: (i) to originate a practical means for prolonged storage of tissues and organs in unfrozen mixed solvent media at subzero temperatures; (ii) to provide a list of cryoprotective nonelectrolytes (such as DMSO, glycerol, etc.) which are relatively nontoxic and effective in preserving tissues without injury; (iii) to eliminate the error due to liquid junction and to provide standard pH data for buffers in water and in mixed solvents, with and without liquid junctions; (iv) to establish a "universal" pH scale based on electrode potentials and pK values.